Metallic abrasive composition of matter



i "I i l Patented Jan. 16, 1945 METALLIC ABRASIVE COMPOSITION OF MATTERHermann Kott, West Orange, N. J., assignor to Fish-Schurman Corporation,New York, N. Y., a corporation of New York No Drawing. ApplicationDecember 28, 1943, Serial No. 515,972

9 Claims.

This invention relates to abrasive compositions of matter and moreparticularly to abrasive and cutting tools comprised of a metallic bodycontaining small particle sized diamonds or other abrasive materialdispersed therethrough, and has for its object the provision of animproved metallic composition for use in said metallic body.

Another object is to provide a tough, strong and substantiallyrust-resistant metallic composition suitable for use as the metallicbody of said abrasive composition of matter.

Another object is to provide a sinterable mixture of metallic powderswhich on heat-treating to elevated temperatures without compaction,sinters or coalesces into a relatively dense, substanti ally non-porous,metal body without excessive shrinkage and which in the heat-treatedcondition is characterized by high strength and ductility, resistance tocorrcsioh and to surface oxidation, and by the surface characteristic ofslipperiness.

Still another object is to provide an imareved metallic abrasivecomposition of matter consisting of a sintered mixture of metal powdersand small sized diamond fragments characterized by having the diamondparticles tenaciously retained in dispersed position throughout themetallic body and by having a relatively dense, tough and strongmetallic body possessing the properties of rust resistance and surfaceslipperiness.

Other objects will be apparent as the invention is more fullyhereinafter disclosed.

In co-pending application Serial No. 488,566, filed May 26, 1943, whichapplication is assigned to the same assignee as the present application,there is described and claimed an abrasive composition comprised ofdiamond fragments dispersed throughout a metallic matrix and method offorming same which consists essentially in surfacing the diamondfragments with a firmly adherent but relatively thin film layer of ametal of the platinum group (specifically rhodium), mixing the coateddiamonds with finely divided metal powder consisting of an iron-carbonalloy containing approximately .87% carbommold ng the mixture to thedesired shape, and heat-treating the molded mixture to a temperatureabove 725 C. but below 800 C. foran extended time interval adapted toconvert the iron-carbon alloy particles into austeniteand to cement thesame together and to form an intermetallic bond between the rhodiumsurface en the diamonds and the cemented iron-carbon alloy.

In the manufacture of abrasive compositions of the type disclosed andclaimed in said co-pending application, considerable difliculty isexperienced in obtaining consistently uniform sized products due to theshrinkage of the molded mixture. This shrinkage may in partbe overcomeby the use of pressure in the molding mixture. However, due to thehardness of the iron-carbon particles. the amount of pressure utilizableis limited to that perforating the relatively thin lilm of rhodiumsurfacing the diamond particles.

I have discovered that by the addition of-one of the metals Mn and Ni,in finely divided powder form, to the iron-carbon alloy in an amountwithin the range 3 to 10% but preferably about 5%, I

the shrinkage characteristic of the molded mixture is of such a loworder that the application of pressure to the molded mixture can besubstantially eliminated, without at the same time detrimentallyaffecting the desired density. Moreover, I have found that Mn and Niadditions within the range specified, materially improve the strengthand ductility of the sintered product.

In addition to the above-mentioned discovery, I have discovered alsothat additions of small amounts of at least one of the metals Cu, Au andAg, together with small fractional percentages of indium, impart to thesintered mixture of iron carbon alloy and Mn or Ni, increased densityand a high resistance to corrosion and to surface oxidation or rustingtogether with a surface physical characteristic known in the art asslipperiness which markedly improve the utility of the sintered metalproduct.

Preferably, the amount of the metals of the group consisting of themetals Cu, Au and Ag, incorporated in the alloy, is maintained as low aspractical to obtain the desired result of rust resistance. In most casesI have found that from .20 to .30% of these metals is adequate for thispurpose, although larger amounts up to 1% do not appear detrimental.

In most cases, also, I have found that mixtures of the metals Cu, Au,and Ag, are somewhat more effective than the individual metals, insofaras imparting rust-resistance to the alloy is ,concerned. Gold and silverin approximately equal percentages and in total amount approximatin 20%have been found to be exceedingly effective in imparting rust-resistingproperties to sintered iron-carbon alloys (C .87%) that containapproximately 5% Mn. Cu, when used alone, must be used in somewhatlarger amounts to obtain equivalent results, for example, about .35% Cu,whereas gold and silver when used alone appear about equally effectivein amounts approximating 25%, Mixtures of Cu with Au and Ag, for example5050 mixtures of each constituent, are slightly less effective than goldor silver or 50-50 mixtures of gold and silver.

The addition of indium to the mixture is primarily for the purpose ofimparting the property of surface slipperiness to the sintered metalbody. In amounts as low as .10% indium, this characteristic isexceedingly pronounced where the amount of the Cu, Au and Ag is held tothe minimum percentage required to impart rustresistance to the sinteredproduct. As the metal, indium, is expensive it is advantageous to employas small a percentage as possible to produce this desired result.

Surface slipperiness of the sintered metal product is highly desirablefor the primary reason that such property prevents the accumulation ofthe abrasion-removed particles of matter in the interstices between theprojecting diamond particles. This materiall extends the abrading lifeof the abrasion surface of the abrasive cognposition of matter of thepresent invention.

In addition to imparting the property of surface slipperiness to thealloy composition of the present invention, indium also imparts hardnessto the metals Cu, Au and Ag, thereby serving to toughen and strengthenthe sintered metallic composition.

It is believed apparent that many different ratios of the metals Cu, Auand Ag to the metal In would be effective for the purposes of thepresent invention, but it is preferred to maintain the total amount ofthese metals as low as possible in the base mixture of iron and Mn or Nimetal powders.

As one specific embodiment of the present in-.

vention, but not as a limitation thereof, the preferred mixture of metalpowders consists of. 10% Au, .10% Ag, 10% In, 5% Mn and the remaindercarbonyl iron powder having a carbon content approximating 37%. Theparticle size of the carbonyl iron powder is, preferably, extremelysmall and should contain'no particles larger than about 400 mesh. Theparticle size of the Mn may be considerably larger than this, butpreferably should be less than about 200 mesh. The particle size of theAu, Ag and In should be as small as possible and should at least pass200 to 300 mesh, in order to facilitate the substantially uniformdispersion of the same throughout the iron metal powder.

This mixture of metal powders, after thorough mixing, for example, in aball mill for an extended time interval, is then mixed with therhodium-surfaced diamond fragments, in the desired relative amountswhich varies somewhat with respect to the particle size of the diamonds.The diamond-metal powder mixture thus obtained after being disposed in amold with slight tamping or compaction sufiicient to eliminate any largevoids and to level off the material in the mold, may then be heated,under substantially nonoxidizing conditions on a slowly risingtemperature gradient to a temperature approximating 750 6. for anextended time interval to sinter the same to a coherent metallic body,care being taken during the early stages of heating to heat quite slowlyto drive off any moisture and surface adsorbed gases from the metalpowders before sintering.

One of the major advantages of the present metallic composition over theiron-carbon alloy of the said co-pending application, lies in the factthat because of the relatively low shrinkage constant of the presentcomposition and relative y high strength and ductility of the same, the

amount of diamond fragments incorporated in the mixture may bematerially increased, thereby obtaining more diamond fragments per unitsurface area than heretofore obtainable.

As an example, where diamond fragments having a particle size passingmesh, but not passing mesh, are employed, the ratio of diamonds to metalpowder may be as low as 1 to 3 whereas with the iron-carbon alloy alonea ratio of 1 to 10 is about as low a ratio as may be used. This resultsin a cutting or abrading surface of greatly increased efficiency.

In the above specific example, nickel ma be substituted in part or inwhole for the manganese. In general, nickel is more effective thanmanganese and may be used in lesser amounts. For example 2 to 3% Niappears to be equivalent to 5% Mn. Preferably, carbonyl nickel powder isemployed.

In the above specific example, the metals gold and silver may bedisplaced by 25% of either gold or silver or .35% Cu or with about 30%of a 50-50 mixture of either Cu and Au or Cu and Ag without essentialdeparture from the invention. Also, indium in amounts greater than .10%and up to .30% may be employed without departure.

Following sintering, I prefer to quench the sintered metal product incold water to harden the same and to prevent oxidation of the prctrudingedges of the diamond fragments.

As an illustration of the non-shrinking properties of the metalcomposition of the present invention various tests have shown that theshrinkage of the metal composition of the specific example givenapproximates 2% when no compacting pressure is applied to the metalpowder in the mold prior to heat-treating. This low shrinkage propertyinhibits or protects the diamond fragments against cleavage fracture.The tenacity with which th diamond fragments are retained in embeddedposition in the metal body subsequently even at quite elevatedtemperatures, indicates also that the sintered alloy composition of thepresent invention has a relatively low 00- efficient of expansion.

To facilitate the removal of the sintered metallic body from the moldafter sintering, the interior surface of the mold is covered withrefractory material such as silica dust, graphite. aluminum oxide, andthe like.

It is believed apparent from the above disclosure that the presentinvention ma be widely modified without essential departure from thesame and all such modifications and adaptations are contemplated as mayfall without the scope of the following claims.

What I claim is: i

1. In an abrasive composition of matter consisting of a metallic basemember containing particles of an abrasive dispersed therethrough, ametallic base member comprised of a metallic composition consisting of asintered mixture of metal powders, said mixture consisting of afractional percentage of at least one of the metals consisting of thegroup Cu, Au and Ag, a small fractional percentage of indium, from 3 to10% of at least one of the metals Mn and Ni, balance iron containing theeutectoid percentage of car- 2. In an abrasive composition of matterconsisting of a metallic base member containing diamond fragmentsdispersed therethrough, a me tallic base member comprised of a metalliccomposition consisting of a sintered mixture of metal powders saidmixture consisting of from .20 to .30 at least one of the metals of thegroup consisting of Cu, Au and Ag, a small fractional percentage ofindium, from 3 to of at least one of the metals Mn and Ni, balance Fecontaining about .87% C.

3. In an abrasive composition of matter consisting of a metallic basemember containing diamond fragments dispersed therethrough, a metallicbase member comprised of a metallic composition consisting of a sinteredmixture of metal powders, said mixture consisting of about Au and Ag inapproximately equal amounts, .10% indium, 5.0% Mn, balance Fe containingabout .87 C.

4. An abrasive composition of matter consisting of a metallic bodyhaving small sized diamond particles dispersed therethrough, saidmetallic body being comprised of a sintered mixture of metal powdersconsisting of atleast one of the metals of the group Cu, Au and Ag in afractional percentage above about .20%, a small fractional percentage ofindium above about .l0%, from 3 to 10% one of the metals Mn and Ni,balance Fe containing the eutectoid percentage of carbon.

5. An abrasive composition of matter consisting of a metallic bodyhaving small sized diamond particles dispersed therethrough, saidmetallic body being comprised of a sintered mixture of metal powdersconsisting of .20 to .30% Au and Ag, .10% indium, 3 to 10% Mn, balanceFe containing about .87% C.

6. An abrasive composition of matter consisting of a metallic bodyhaving small sized diamond particles dispersed therethrough, saidmetallic body being comprised of a sintered mixture of metal powdersconsisting of .20 to .30% Au and Ag, .10% indium, 5% Mn, balance Fecontaining about .87% C.

7. The method of forming an abrasive composition of matter consisting ofa mixture of small sized diamond fragments and metal powders sinteredtogether which comprises forming a mixture of metal powder consisting of.20 to .30% at least one of the metals Cu, Au and Ag, about .10% indium,from 3.0 to 10.0% one of the metals Mn and Ni, balance carbonyl ironpowder containing the eutectoid percentage of carbon having a particlesize passing about 400 mesh, the particle sizes of the other said metalsbeing small passing at least about 200 mesh, incorporating in saidmixture the desired percentage of said diamond fragments, disposing themixture in a mold to shape the same, heat-treating the mixture on aslowly rising temperature gradient to elevated temperaturesapproximating -'750 C. in a substantially non-oxidizing atmosphere foran extended time interval, and quenching the heat-treated product torapidly cool the same to atmospheric temperatures. I

8. The method of formingan abrasive composition of matter consisting ofdiamond particles dispersed throughout a metallic matrix which comprisesforming .a mixture of metal powders consisting of .20 to .30% at leastone of the metals Cu, Au, Ag, about .10% indium, from 3 to 10% one ofthe metals Mn and Ni, balance carbonyl iron powder containing theeutectoid percentage of carbon having a particle size passing about 400mesh, the particle sizes of the other said metals passing at least about200 mesh, incorporating in said mixture in the desired amount sizeddiamond particles surfaced with a firmly adherent relatively thin filmof a platinum group metal, disposing the said mixture in a mold to shapethe same, heat-treating the mixture on a slowly rising temperaturegradient to elevated temperatures approximating, 750 C. in asubstantially non-oxidizing atmosphere for an extended time interval,and quenching the heat-treated product to rapidly cool the same toatmospheric tem-' peratures.

9. The method of forming an abrasive composition of matter consisting ofsized diamond particles approximating 120 mesh dispersed throughout ametallic matrix which comprises surfacing the said diamond particleswith a firmly adherent relatively thin film coating of a plati num groupmetal, forming a mixture of metal powders consisting of .20 to .30% amixture of about equal amounts of gold and silver, .10% indium, about 5%Mn, balance carbonyl iron powder containing about the eutectoidpercentage of carbon, the particle size of the said iron powder beingbelow about 400 mesh and the particle sizes of the other said metals notbeing greater than about 200 mesh, mixing the said diamond fragments andmetal powder mixture together in the relative proportions of 20% andrespectively, disposing the mixture in a mold to shape the same, heatingthe said mixture on a slowly rising temperature gradient to elevatedtemperatures approximating 750 C. for a time interval adapted to sinterthe mixture together into a coherent metallic body, and quenching thesaid body to rapidly cool the same to atmospheric temperatures.

HERMANN KO'I'I.

